We had a 10M unit attached to our machine back in 1964.  It weighed in at just over 3/4 ton.  49 heads arranged along the drum matched the 49-bit machine it hooked to.  The 49th bit was a parity bit.
We scrapped that after a year and went with a Burroughs D82 with a D825 Front end to handle 36 incoming and 24 outgoing TTY channels.  All our programming was with punched cards.
Fun times.
Bill